Electrode assembly



1959 R. .1. BONDLEY ET AL 2,900,541

ELECTRODE ASSEMBLY Filed Nov. 14, 1956 In ve r t 0 rs: Pa/ph J Bond/ey, WIN/am H Tea r 4 PM 4% The j'r Azsoi United States Patent 2,900,541 ELECTRODE ASSEMBLY Ralph J. Bondley, Scofia, and William H. Teare, Ballston Lake, N.Y., assignors to General Electric Company, a corporation of New York Application November 14, 1956, Serial No. 622,226

Claims. (Cl. 313-32) The present invention relates to an improved electrode assembly for electron discharge devices and more particularly to an improvedfluid-cooled accelerating electrode assembly for electron beam devices.

In electron discharges and particularly in high voltage electron beam discharge devices, it is common practice to use an accelerating electrode rather closely However, molybdenum presents some difiiculties because of the rather large diiference in temperature coefficient of expansion of molybdenum compared with those materials usually used in the construction of the metal parts of the tube and particularly when used adjacent copper or stainless steel parts, copper being a very desirable metal from the standpoint of heat transfer.

Accordingly, it is an important object of the present invention to provide improved electrode assembly offering the advantages of a molybdenum surface in the region of high electric field and thereby exhibiting a minimum tendency to spark over in operation, and at the same time providing good mechanical support and good heat transfer from the anode to the supporting structure.

In accordance with the illustrated embodiment of our invention, the accelerating anode is a molybdenum disk supported from the face of a copper body by means of a plurality of concentric circular arrays of relatively small segments, extending from one side of the body, the opposite side of the disk being in good heat transfer. relationship with a plurality of passages for cooling fluid.

Further objects and advantages of our invention will become apparent as the following description proceeds, reference being had to the accompanying drawing and its scope will be pointed out in the appended claims.

In the drawing,

Fig. l is an elevational view partially in section of an electron beam tube of the velocity modulation type showing an electrode assembly embodying our invention;

Fig. 2 is an enlarged sectional view of a portion of the device of Fig. 1;

Fig. 3 is a sectional view taken along the line 3-3 of Fig. 2, and

Fig. 4 is a sectional line taken along the line 4-4 of Fig. 2.

In Fig. 1 of the drawing, I have shown our invention incorporated in an accelerating electrode assembly 1 for an electron beam tube of the velocity modulation type. The tube includes a cathode having a concave emitting surface 2 surrounded by a focusing cup 3 terminating in a rolled edge 4 opposite and closely spaced to an annular accelerating electrode 5. Both the cathode cup 3 and the accelerating electrode 5 are preferably formed of molybdenum in accordance with the present invention. The cathode is heatedv by a suitable resistance type heater illustrated schematically at 6 and having one terminal thereof insulated from the cathode and connected to a lead-in conductor 7. Theother terminal is connected to the cathode cup 3 which is in turn connected to a metal terminal 8 insulated from the cylindrical envelope member 9, the latter member preferably being formed of stainless steel. Electrons from the emitting surface are accelerated by the electrode 5 and pass through the opening therein through a drift tube 10 into an input or modulating cavity 11. Electrons pass from cavity 11 through another drift tube 12 into a second cavity 13 which may be the output cavity of the device. As will be well understood by those skilled in the art, electrons passing through cavity 13 are collected by a suitable collector electrode not shown.

The electrode assembly embodying the present invention will be better understood by a consideration of Figs. 2, 3 and 4 which showed enlarged sectional views of the structure of this assembly. As mentioned in the earlier discussion, the drift tube 10 is preferably of copper, at least partly because of its good heat transfer characteristics. Also the envelope cylindrical portion 9 may be to advantage formed of stainless steel, partly because of its strength and partly because its temperature coefficient of expansion matches reasonably well with that of copper and facilitates the joining of this envelope part to a flange 14 on a recessed apertured disk 15 which is formed 'of copper and which is suitably brazed to the drift tube 10. a

The electrode assembly for supporting andcooling accelerating electrode 5' includes annular supporting disk 16, preferably of copper, and a cooling disk 17. In order to accommodate the diiference in thermal expansions of the accelerating electrode 5 and the copper supporting disk 16, the disk is provided with a plurality of circular arrays of annular segments 18, extending from one surface'thereof. These segments may be produced by milling circular and radial slots into the face of the disk and then brazing the molybdenum electrode to the segments. As best shown in Fig. 4, the inner ring 19 is not provided with radial slots and as a result provides a smooth surface defining the beam path as it enters the drift tube 10. This narrow ring is not of suffici'ent area to cause difficulty due to the differences in expansion of the members and could be slotted radially if such difficulties were encountered.

In order to eflfect the transfer of heat from the accelerating anode 5, the disk 17 which in turn supports the disk 16 is provided with a plurality of circular arrays of semi-circular baffles 20 with the openings 21 between the adjacent ends of the baffles in adjacent arrays being displaced by This provides a circuitous path between an inlet passage 22 for cooling fluid and the outlet passage 23. While the disk 16 and 17 have been made in separate pieces in order to facilitate manufacture and then brazed together and to the drift tube and flange 15, it is readily apparent that these two parts may be made in one piece if desired. As indicated in Fig. 3 of the drawing, the central openings in the disk 16 and 17 are frustroconical to provide a tapered entrance passage to the drift space 10.

With the construction just described, it is possible to select the material of the accelerating electrode for its desired electrical properties and, as previously mentioned, molybdenum exhibits the best properties for use in a high voltagetube of this type, exhibiting the least tendency to spark over under high electric field conditions. Also, a support is provided which takes care of the difference in expansion between the molybdenum and the other components of the tube, such as the stainless steel wall and the copper flange 15. The use of copper also provides for the elficient transfer of heat to While we have described and illustrated a particular 5 embodiment of our invention, it will be apparent to those skilled in the art that changes and modifications may be made without departing from our invention in its broader aspects. We aim, therefore, in the appended claims to cover all such changes and modifications as fall within the true spirit and scope of our invention.

What we claim as new and desire to secure by Letters Patent of the United States is:

1. An electrode assembly for an electron discharge device comprising an aperturedmetal body, said body having a plurality of concentric circular arrays of annular segments extending from one surface thereof and an annular ring of a difierent metal bonded to said annular segments, said segments providing a yieldable connection between said electrode and said body to accommodate diflferences in thermal expansion of said two metals.

2. An electrode assembly for'an electron discharge device comprising an apertured metal body, said body being recessed from one face to provide a plurality of articulated segments and a ring of a difierent metal brazed to said segments, said segments providing a yieldable connection between said electrode and said body to accommodate diiferences in thermal expansion of said two metals. 7

3. An accelerating electrode assembly for an electron beam type of discharge device comprisingan-apertured copper body, said copper body having a plurality of concentric circular arrays of annular segments extending from one surface thereof and an annular ring of molybdenum brazed to said annular segments, said segments providing a yieldable connection between said electrode and said body to accommodate difierences in thermal expansion of said two metals.

4. An electrode assembly' c omprising an apertured molybdenum disk, a support for said disk comprising a generally annular copper body recessed from one face to provide a plurality of concentric circular arrays of annular segments and recessed from the opposite side to provide a plurality of passages for cooling fluid,,said segments being brazed to said molybdenum disk and providing with 'said segments a yieldable connection between said molybdenum disk andsaidcopper body.

5. An electrode assembly comprising an apertured metal disk electrode, a support for said electrode comprising a generally annular body of a second metal having a different temperature 'coefiicient of expansion than the metal of said electrode recessed from one face to provide a plurality of articulated segments and recessed from the opposite side to provide a plurality of passages for cooling fluid, said segments being bonded to said electrode to provide a yieldable connection between said electrode and said body.

References Cited in the file of this patent UNITED STATES PATENTS 1,943,250 Widmer Jan. 9, 1934 2,296,885 Vance Sept. 29, 1942 2,739,262 Watrous Mar. 20, 1956 2,751,662 Glenn et a1. June 26, 1956 2,757,314 Sheppard et al. July 31, 1956 2,821,651 Werner a Jan. 28, 1958 

